Post on 28-Jan-2015
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Climbing Mount Android
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Rajesh Vasa, 2011
Twitter: @rvasahttp://www.rvasa.com
R. Vasa, 2011
Mobile Eco-System
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Ad Networks
Platform
Content Providers(Music/Video/Books)
Handset OEMs
Telephone Networks
App. Distribution
Cloud Infrastructure
Billing
R. Vasa, 2011
Android Eco-System
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Ad Networks
Platform
Content Providers(Music/Video/Books)
Handset(OEMs)
Telephone Networks
App. Distribution
Cloud Infrastructure
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Google, Double Click
Google, Amazon
Android
Google, Amazon
Samsung, HTC, Motorola, Sony ...
Billing
Google Checkout
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Focus of this talk...
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Ad Networks
Android Platform
Content Providers(Music/Video/Books)
Handset(OEMs)
Telephone Networks
App. Distribution
Cloud Infrastructure
**
Google, Double Click
Google, Amazon
Google, Amazon
Samsung, HTC, Motorola, Sony ...
Billing
Google Checkout
This talk will present a development perspective
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Talk Overview
•Devices
•What is Android?
•Development Tools
•The Android Way
•Anatomy of a Simple Android Application
•An Interactive Android Application
•Dealing with Multiple Activities
•Activity Life Cycle (the odd thing)
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R. Vasa, 2011
Roadmap - Where are we?
•Devices
•What is Android?
•The Android Way
•Anatomy of a Simple Android Application
•An Interactive Android Application
•Dealing with Multiple Activities
•Activity Life Cycle (the odd thing)
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Android Device User Interaction
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Menu
HomeBack
Android devices have three key buttons
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Vendors can add additional buttons
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There are variations in physical form
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But all phones have Home, Menu, & Back Buttons
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Home Button...
•Typically, this will take you back to the Home Screen of the phone
•Default behaviour ~ iPhone / iPad button
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Home
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Back Button
•This will take you back to the previous screen
•If app. has only one screen, this will exit app.
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BackPersonal Opinion: iPhone / iPad should borrow this button
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Menu Button
•Shows a contextual menu (if one is available)
•Developers can write their own menus
•Quite handy (but, causes Usability issues)
• Low Discoverability
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Menu (as open)
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Android for tablets is slightly different...
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Back, Home
Where is the menu button?
Action Bar
(Buttons need not be physical in Android)
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Tablet Menu Icon Visibility is contextual
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Menu
Sadly, menu position is not mandated (yuk?)
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Roadmap - Where are we?
•Devices
•What is Android?
•Development Tools
•The Android Way
•Anatomy of a Simple Android Application
•An Interactive Android Application
•Dealing with Multiple Activities
•Activity Life Cycle (the odd thing)
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What is Android?
•Android is a platform
•Operating System (with primitive API)
• Frameworks (incl. components and libraries)
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Applications
Operating System(Customised Linux Kernel)
Android Frameworks
API
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Android
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Image Source: http://developer.android.com
Programming languages: Java, C/C++
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Android is a bi-lingual platform
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Image Source: http://www.tbray.org
JavaC/C++
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Most Android Code is in Java (but...)
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Android Java is not 100% Sun Java
≠
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Android Java is different (in many ways)
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No RMI
No Bytecode
No AWT / Swing UI
Different 2D/3D libs
Different Class Load Mechanism
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Roadmap - Where are we?
•Devices
•What is Android?
•Development Tools
•The Android Way
•Anatomy of a Simple Android Application
•An Interactive Android Application
•Dealing with Multiple Activities
•Activity Life Cycle (the odd thing)
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Development Tools
•Android SDK (Compiler and Emulator)
•Eclipse IDE + Android Plug-in
•Powerful debugger
•Visual UI Builder
•Ant (Build System)
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Download from http://developer.android.com
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Eclipse IDE
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Eclipse IDE - Graphical UI Editor
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Android Emulator
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Permits checking Portrait and Landscape views
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Emulator is nice .. but phone is better
•The emulator runs the Android O/S (you can run any version: 1.6 to 3.0)
•Emulates the phone hardware (like VM Ware)
•Emulator does not have sensors (e.g. GPS, Gyro, Accelerometer, Cell phone etc.)
• It however offers ways to simulate these events
• So, I can send an SMS to the emulator or make a phone call to it
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Emulators Vs Simulator
•iOS offers a simulator
•Android has gone down the emulator path
•Trade-offs (pros and cons),
• Simulators start-up faster, good enough
•Emulators allow checking against rel. 1.6 of the O/S easily + closer to phone hardware
•Emulators and Simulators cannot mimic real CPU speed, disk speed, network speed etc. (yet!)
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If your Java is rusty
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Free e-Book: http://www.mindview.net/Books/TIJ/
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Roadmap - Where are we?
•Devices
•What is Android?
•Development Tools
•The Android Way
•Anatomy of a Simple Android Application
•An Interactive Android Application
•Dealing with Multiple Activities
•Activity Life Cycle (the odd thing)
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The Android Way
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Convention
Configuration
Development is organised around a few conventions
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Android Project Structure (convention)
•Source code (src)
•Generated code (gen)
•Resources (res)
•Images (drawable)
•Layout of app (layout)
•Constants/Strings (values)
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Needs Resources @Multiple Resolutions
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High
Low
Medium
Convention
R. Vasa, 2011
Roadmap - Where are we?
•Devices
•What is Android?
•Development Tools
•The Android Way
•Anatomy of a Simple Android Application
•An Interactive Android Application
•Dealing with Multiple Screens (Activities)
•Activity Life Cycle (interesting design choice)
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A Simple Android App.
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What is involved?
•Place UI controls (Text and Image)
•Layout the controls
•Centre text
•Make text large font
•Display Image to take up all space
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Each Screen is an Activity
•Android app. is made up of Activities
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Activity
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Views are Android’s Key UI Building Block
•We need two views on the Activity
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TextView
ImageView
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Views are Placed inside a View Group
•Different types of pre-defined layouts
• Linear, Relative, Table, Frame etc..
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View Group
a.k.a Layout
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Android App. - Building Blocks
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Activity Layout Views(View Group)
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Separation of Concerns in Android
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Presentation Functionality
Layout Definition (main.xml)
Activity Class
Event Handling, I/O ...
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UI (Layout) Definition
•Layout definition is generally in an XML file
•Hand coded or Visual Editor
•Can be also be done in Java Code (yuk!)
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Layout Definition XML File
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Android Offers a number of UI Controls
•Offers all standard controls and lot more...
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Progress
These are a small
subset of available controls
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View Groups and Layouts
•Android offers the following View Groups,
• Linear Layout (Horizontal or Vertical)
•Absolute Layout (You set X, Y for each View)
•Table Layout (Rows and Columns)
•Relative Layout (Position relative to other Views)
• Frame Layout (Show only one view at a time)
• Scroll View (Permits scrolling of the screen)
•View Groups can be nested
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Generated Code, Layout & Resources
•How did Australia image get into the App.?
•How did we set the text to “Australia”?
•Conventions
• Layout Defined in /layout/main.xml
•Resources Placed in /res/drawable-*
• String values defined in /values/strings.xml
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Resources
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Resources in “res”
Convention
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Resources are given a unique ID
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A unique reference id to resources is
generated by the Android SDK tools
Convention
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Resources and Generated IDs
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Generated Code
static final int australia=0x7f020000;
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A Reference to Layout also Generated
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All References are Integers
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Identifiers are used to access resources
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Reference to the layout
This is the Activity Class
(Android Runtime will Render this Layout)
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Layout is Referred to from Java Code
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Activity
View Group(Layout)
Activity Class (Java)
Layout Definition (main.xml)
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Who writes the Activity code?
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This block of code is created by IDE/SDK when we create new Android project
You can also write you own
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Activity Creation
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Method called (by Application Launcher) when App is first launched
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Activity Creation - Layout Rendering
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Method call will pass the reference to the layout that needs to be rendered on the screen
(“Rendering” is a two-pass process: measure and draw)
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What is the “root” Activity?
•How does Android know which Activity to create first?
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Answer: Application Manifest File
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Application Manifest File
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Activity Name
Application Icon Reference
Category
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Application Manifest File
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Category indicates that it can be launched
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Application Manifest File
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Main action indicates that it is the starting point
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Layouts and String Information
•How did we set the text to “Australia”
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String constant
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Using Graphical Resources
•How did the Australia image get into layout?
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Layout can refer to resources
@drawable is a special tag
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What is it with the @ tag?
•Constant Resources in Android can be referred using the “@” tag in XML layout
•Example: @drawable, @string ...
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@drawable/australia
@drawable/bots
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@ Tag and Multiple Screen Resolutions
•Dealing with multiple screen resolutions
@drawable/icon
Android Runtime decides best resource to use based on hardware capabilities
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Significance of hdpi/ldpi/mdpi
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High-Res, 240 dpi screen
Low-Res, 120 dpi screen
Med-Res, 160 dpi screen
Different resolution images
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Roadmap - Where are we?
•Devices
•What is Android?
•Development Tools
•The Android Way
•Anatomy of a Simple Android Application
•An Interactive Android Application
•Dealing with Multiple Screens (Activities)
•Life Cycle & interesting design choices
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Building an App with Simple Interaction
•Temperature Conversion (C -> F)
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Views
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TextView
EditText
Button
TextView
4 Views (UI components) using a Linear Layout
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Linear Layout (View Group)
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main.xml(Layout)
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View Identifiers
•We need a way to identify components that we created in the layout
•E.g. To read input data from the field
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@+id TAG creates new identifiers
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UI Interaction Handling Pattern
•Component.setOn......Listener ( handler )
•E.g. button.setOnClickListener
•Handler is an anonymous inner class
•On...Listener handler = new On....Listener() {}
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UI Interaction Handling Pattern
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The View identifiers are defined in XML
R. Vasa, 2011
Roadmap - Where are we?
•Devices
•What is Android?
•Development Tools
•The Android Way
•Anatomy of a Simple Android Application
•An Interactive Android Application
•Dealing with Multiple Screens (Activities)
•Life Cycle & interesting design choices
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Wiring up Multiple Activities
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Select
Back
Contact List Activity Contact Details
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Activities are Stacked in Android
•All current activities are placed on a Stack
•Newly started activities come into foreground
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Contact List
Contact Details
Foreground/Active
starts Background/Paused
Back button will pop top most
activity from stack
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Activities are like mini-processes
•Android activities have their own life cycle
•Communication between Activities is done by Asynchronous Messaging
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Contact List Contact Detailsmessage
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Async. messaging called “Intents”
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Contact List Contact Detailsintent
Activities communicate with each other via Intents
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Async. messaging called “Intents”
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Activity-X Photo Viewerview photo
intent
You can send a general purpose message (intent), all applications capable of handling that Intent will respond
Framework prescribes conventions for common intents
R. Vasa, 2011
Roadmap - Where are we?
•Devices
•What is Android?
•Development Tools
•The Android Way
•Anatomy of a Simple Android Application
•An Interactive Android Application
•Dealing with Multiple Screens (Activities)
•Life Cycle (& interesting design choices)
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Android Activities are Managed by O/S
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Activity-A
Activity-C
Activity-B
ApplicationActivities have a
parent application
Activity has Life Cycle Application is NOT managed
directly by the O/S
Life Cycle is Managed by Android Framework
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Android Activity Life Cycle
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Activity is re-started when orientation changes
Developers have to save and retrieve state if orientation changes
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Security -- Android Devices
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AndroidApplication
User UID (User ID)has
also has
The UID is generated at install time based on the signature and package name
File System Access Permissions
determines
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A Short Plug!!!
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Mobile Development @ Swinburne
•HIT8328 - Software Development for Mobile Devices
• Android focused
•HIT8329 - Creating Data Driven Mobile Applications
• iOS focused
• Portfolio Based Assessments
• We do not just cover API -- there is a strong conceptual foundation (prepare you to learn)
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We Offer Options to Study Just One Subject
Teaching material will be available openly shortly
R. Vasa, 2011
Mobile Development @ Swinburne
•HIT8328 - Software Development for Mobile Devices
•HIT8329 - Creating Data Driven Mobile Applications
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Teaching material will be available under an open license shortly
Follow @rvasa or @swinfict for update